Process for oxidizing a 1 1-bis(alkylphenyl) alkane

ABSTRACT

A PROCESS FOR OXIDIZING A 1,1-BIS(ALKYLPHENYL)ALKANE, WHEREIN THE ALKANE BRIDGE HAS AT LEAST TWO CARBON ATOMS, TO CONVERT ALKYL SUBSTITUENTS TO CARBOXYLIC ACID SUBSTITUENTS WHICH INVOLVES CONTACTING THE 1,1-BIS-(ALKYPHENYL) ALKANE WITH OXYGEN IN A LOWER CARBOXYLIC ACID CONTAINING COBALT AND AN ALIPHATIC HYDROCARBON HAVING FROM THREE TO SIX CARBON ATOMS.

United States Patent U.S. Cl. 260-524 R Claims ABSTRACT OF THE DISCLOSURE A process for oxidizing a 1,1-bis(alkylphenyl)alkane, wherein the alkane bridge has at least two carbon atoms, to convert alkyl substituents to carboxylic acid substituents which involves contacting the 1,1-bis-(alkylphenyl) alkane with oxygen in a lower carboxylic acid containing cobalt and an aliphatic hydrocarbon having from three to six carbon atoms.

This invention relates to a process for oxidizing a 1,1- bis alkylphenyl alkane.

In U.S. Pat. No. 3,424,789 of Schulz et al., a 1,1-bis- (alkylphenyl)alkane was subjected to oxidation by contacting the same at elevated temperatures with molecular oxygen in the presence of a transition metal salt of a carboxylic acid and methyl ethyl ketone. Unfortunately, not all of the alkyl substituents on the phenyl rings were com verted to carboxylic acid substitueuts and it was found necessary to complete the conversion of the alkyl substituents by subjecting the initially oxidized product to further oxidation with nitric acid. In addition, in each case the 1,1-bis(alkylphenyl)alkane was converted to the corresponding benzophenone.

It has been found that when the process defined above is carried out in the presence of an aliphatic hydrocarbon and a lower carboxylic acid, each of the alkyl substituents on the phenyl ring can be converted to a carboxylic acid substituent and, surprisingly, the alkane bridge is substantially unaffected and little or no 'benzophenones are obtained.

The l,1-bis(alkylphenyl)alkane that is subjected to treatment herein is one wherein each phenyl group carries from one to five alkyl groups, preferably from one to two alkyl groups, each alkyl group having from one to 16 carbon atoms, preferably from one to eight carbon atoms, and said alkane bridge has from two to 16 carbon atoms, preferably from two to eight carbon atoms. of these, 1,1-bis(alkylphenyl)alkanes are preferred. Specific examples of 1,l-bis(alkylphenyl)alkanes that can be employed include 1,1-bis(p-tolyl) ethane, l,1-bis(p-tolyl) propane, 1,1-'bis(p-to1yl) butane,

1, l-bis (p-tolyl) hexane, 1,1-bis(p-tolyl)octane, 1,1-bis(p-tolyl) decane, 1,1-bis (p-tolyl dodecanc, 1,1-bis(p-tolyl) tetradecane,

1,1-bis (p-tolyl) hexadecane,

1,1-bis (4-ethylphenyl) ethane, 1,1-bis(4octylphenyl)pentane, l,1-bis(4-decylphenyl) octane, 1,1-bis(4-hexadecylphenyl)hexadecane, 1,1-bis(3 ,4-dimethylphenyl ethane,

'1,l-bis(3,4-dimethylphenyl) propane,

1,1-bis(3,4-dimethylphenyl)butane, 1,l-bis(3,4-dimethylphenyl)hexane, 1,1-'bis( 3,4-dimethylphenyl) octane,

3,641,135 Patented Feb. 8, 1972 ,l-bis 3,4-dimethylphenyl) decane,

,1-bis(3,4-dimethylphenyl) dodecane,

, l-bis 3 ,4-dimethylphenyl) tetradecane,

,1-bis(3,4-din1ethylphenyl)hexadecane,

, l-bis 3,4-diethylphenyl ethane,

, 1 -bis 3,4-dioctylphenyl) pentane,

,1-bis(3 ,4-didecylphenyl octane,

,1-bis(3,4-dihexadecylphenyl)hexadecane,

l-bis (2,2-dibro mo-3,4,3 ,4'-tetramethylphenyl) ethane, (3-methyl-4-ethylphenyl) 2'-nitro-3 ',4'-diethylphenyl ethane,

, l-bis (3 ,4,3 ',4'-tetramethyl-S-aminophenyl) ethane,

- 3,4-diethylphenyl 3 ',4'-diisopropylphenyl) ethane,

- 2-methyl-4-isopropylphenyl) -(4-methyl-2-nitrophenyl ethane,

1,1-bis (3-ethyl-4-butylphenyl) isobutane,

l- (4-propylphenyl) 1- Z-ethylphenyl) octane,

1, l-bis- 2,4-diisopropylphenyl)hexadecane,

1, l-bis (2-ethyl-4-butylphenyl) isobutane, etc.

The reaction defineed herein can be carried out by bringing together the 1,1-bis(alkylphenyl)alkane, molecular oxygen, cobalt, the aliphatic hydrocarbon and a lower carboxylic acid at moderate temperatures and pressures.

The molar amount of molecular oxygen needed is 1.5 mols for each alkyl substituent converted to carboxylic acid substituent. To assure the desired oxidation about one to about molar excess of molecular oxygen can be used.

Also present in the reaction mixture is cobalt, which can be added in an form, but is preferably added as a salt soluble in the reaction mixture. Thus, the cobalt compound can be in the form of an inorganic compound or as an organic compound, for example, as a cobaltous or cobaltic chloride, sulfate, nitrate, acetate, propionate, butyrate, isovalerate, benzoate, toluate, naphthenate, salicylate, acetyl acetonate, etc. The amount of cobalt compound employed, as cobalt, based on the total reaction mixture is from about 0.1 to about 15 percent, preferably from about 0.3 to about five percent by Weight.

Additionally required herein is an aliphatic hydrocarbon having from three to six carbon atoms, preferably four carbon atoms, such as propane, n-butane, n-pentane, n-hexane, cyclohexane, cyclopentane, etc. Of these, normal butane is preferred. The amount of aliphatic hydrocarbon can be from about 0.001 to about 1000 mols per mol of 1,1-bis(alkylphenyl)alkane, preferably from about 0.1 to about two mols per mol of 1,1-bis(alkylphenyl) alkane. In those situations wherein it is desired to reduce the induction period, a promoter such as a methylenic ketone can also be added to the reaction system. Methylenic ketones which can be employed are methyl ethyl ketone, methyl propyl ketone, diethyl ketone, acetylacetone, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, l-tetralone, Z-tetralone, l-decalone, Z-decalone, etc. Of these, methyl ethyl ketone is preferred. The amount of such activator can be from about 0.1 to about 50 mols, per mol of 1,1-bis(alkylphenyl)alkane, preferably from about 0.5 to about five mols per mol of 1,1- bis alkylphenyl) alkane.

Also required in the reaction zone is a lower carboxylic acid, that is, one having from two to six carbon atoms, preferably from about two to four carbon atoms. Specific examples of such lower carboxylic acids that can be used include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, etc. Of these acetic acid is preferred. The amount of carboxylic acid used can vary over a wide range, but on a weight basis, relative to the l,l-bis(alkylphenyl)alkane, can be from about 1:1 to about 50:1, preferably from about 5:1 to about 20:1.

Reaction conditions are mild. Thus, the temperature can be from about 60 to about 200 0., preferably from about 90 to about 125 C., and the pressure can be from about atmospheric to about 5000 pounds per square inch gauge, preferably from about 100 to about 500 pounds per square inch gauge. A residence time of about one minute to about 60 hours, preferably from about two to about 12 hours, can be used.

The desired diphenyl alkane acids can be recovered from the reaction mixture in any convenient manner. For example, at the end of the reaction period the reaction product is cooled to atmospheric conditions, resulting in the precipitation of diphenyl alkane acids. Upon filtration, the desired diphenyl alkane acids are easily recovered.

The process can further be illustrated by the following example.

EXAMPLE i Into a glass flask there was placed 400 grams of glacial acetic acid and '20 grams of cobaltous acetate tetrahydrate. While maintaining the contents of the flask at 100 C. and atmospheric pressure, molecular oxygen was passed therethrough at a rate of 100 cubic centimeters per minute over a period of 36 hours. Into a one liter, 3l6-stainless steel, magnetically-stirred autoclave there was added the contents of the flask, 400 grams of glacial acetic acid, 74 grams of normal butane and 39 grams of 1,1-bis (p-tolyl) ethane (DTE). The contents of the autoclave were raised to 106 C. and pressured with molecular oxygen to 330 pounds per square inch gauge. The contents of the autoclave were maintained under these conditions for 5.5 hours. The autoclave was then depressured, cooled to room temperature and filtered to recover 16.0 grams of solid as first crop. The filtrate was evaporated to dryness and then extracted with acetone. The residue was treated with concentrated hydrochloric acid, washed with water and then filtered to obtain a second crop of 16.5 grams. The acetone fraction was evaporated to dryness, resulting in 12.0 grams of a third crop. The total product was analyzed by gas chromatography and was found to contain 31.4 grams (62.9 percent yield) of the diphenyl ethane dicarboxylic acid and 8.0 grams (18 percent) of the diphenyl ethane monocarboxylic acid. The product obtained herein was additionally analyzed by infrared and nuclear magnetic resonance spectroscopy, neutral equivalent and melting point.

EXAMPLE II In each of several runs there was introduced into a one-liter, 31'6-stainless steel, magnetically-stirred autoclave glacial acetic acid, cobaltous acetate tetrahydrate, a promoter, an aliphatic hydrocarbon and either l,l-bis(ptolyl)-ethane (DTE), 1,l-bis(3,4-dimethylphenyl)ethane (DXE), or bis-(3,4-dimethy1phenyl)methane (DXM). The autoclave was raised to reaction temperature, pressured with molecular oxygen and maintained under these conditions for a defined period of time. At the end of the reaction period, the autoclave was depressured and cooled and the solid diphenyl alkane acids were recovered by filtration. Recovery of the overall products varied from about 75 to about 95 percent. Analysis was made in accordance with the procedures defined in Example I. The results obtained are tabulated below in Table I.

The results obtained above clearly show the uniqueness of the procedure defined herein. Note that when DTE. and DXE, both compounds having an alkane bridge containing two carbon atoms, were subjected to the defined oxidation procedure, substantially all of the product obtained was a diphenyl ethane carboxylic acid, but that in Run No. 6, when DXM, a compound having but one carbon in the alkane bridge was subjected to oxidation, a large part of the product was a benzophenone acid. In each of Runs Nos. 1 to the yield to benzophenone acids was five percent or less and the yield to cleavage products ranged from five to percent.

TABLE I Selectivity, percent (grams) 120- Reaction conditions Charge Oxygen pressure,

Colbaltous ethane methane methane methane monocerethane monoear- Aromattricarboxylie acid to pounds Reaction Percent dieardicar- Aliphatic hydro- Temp per square time, charge conboxylicboxylie boxylic boxylic Initiator Grams hydrocarbon Grams carbon 0.) inch gauge hours vetted acid acid acid acid* Run No.

Grams I I I I I I, I I I I I I I I I I I I I I I I I I I I I I I vI I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I Ev? A N 3m v vw m s .N em:

be no H Iii Q O me [\Q (2 mm In 7 0 oi 14:15 In cow F11 mm B, BB Q QQ nc 8 I I-I F.

I :05 i= IQ o E5 5:: "1% 6.4: Z IO I 3 l5 I-I. I I

I Ioo Imagodad- IU @031 I 2 I0 Co a mm 6 s0 0 7-4 new I I I I I I I I I I .I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I No:

I I I I I I I I I i I I I I l I I I I -l I I I 2 l I I l I I I I l '51 'o? 3 & :o 9

A A 1 '3 :0 v v a c or 0' 8 8 PI PI 0 N no N o c c a m t: In 3 3 w on H E M o a $3 I-I ES 3 Es 2 Q 2 a e 7 so I as -I-II--I ghwsd ceas QQQM 2 I I O c o: o:

a% IO. N

I I l I -I I I I I l I l I I I I I I I- I l I I I I I I I l a In butane. 6- n 20 do 25 do. 60 percent was the dialkane' diaeidg 40 percent was the benzophenone diacid.

80 DXM The diphenylethane polycarboxylic acids obtained herein can be used to react with polyhydric alcohols, such as ethylene glycol, or with diamines, such as hexamethylene diamine, to obtain polyesters and polyamides, respectively, which are useful in the preparation of fibers or plastics. The diphenylethane monocarboxylic acids can be further oxidized in accordance with the procedure defined herein to obtain diphenylethane polycarboxylic acids or they can be used in combination with the diphenylethane polycarboxylic acids in the reactions defined above to terminate the reaction of the diphenylethane polycarboxylic acids with the polyhydric alcohols or with the diamines.

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for oxidizing a 1,1-bis(alkylphenyl)alkane, wherein the alkane bridge has from two to 16 carbon atoms, to convert alkyl substituents on the phenyl rings to carboxylic acid substituents without affecting said alkane bridge which comprises contacting said l,l-bis(alkylphenyl)alkane with molecular oxygen in a lower carboxylic acid containing cobalt and an aliphatic hydrocarbon havin g from three to six carbon atoms.

2. The process of claim 1 wherein said l,1-bis(alkylphenyl)alkane is 1,1-bis(p-tolyl)ethane.

3. The process of claim 1 wherein said l,1-bis(alkylphenyl)alkane is 1,l-bis(3,4-dimetl1y1phenyl)ethane.

4. The process of claim 1 wherein said lower carboxylic acid has from two to six carbon atoms.

5. The process of claim 1 wherein said lower carboxylic acid has from two to four carbon atoms.

6. The process of claim 1 wherein said lower carboxylic acid is acetic acid.

7. The process of claim 1 wherein said lower carboxylic acid and said 1,1-bis(alkylphenyl)alkane are present in a weight ratio of about 1 :1 to about 50:1.

8. The process of claim 1 wherein said lower carboxylic acid and said 1,1-bis(alkylphenyl)alkane are present in a weight ratio of about 5 :1 to about 1.

9. The process of claim 1 wherein said cobalt is obtained from a cobalt salt soluble in the reaction mixture.

10. The process of claim 1 wherein said cobalt is obtained from cobaltous acetate tetrahydrate.

11. The process of claim 1 wherein the amount of cobalt employed is from about 0.1 to about 15 percent by weight based on the total reaction mixture.

12. The process of claim 1 wherein the amount of cobalt employed is from about 0.3 to about five percent by weight based on the total reaction mixture.

13. The process of claim 1 wherein said aliphatic hydrocarbon is normal butane.

14. The process of claim 1 wherein said aliphatic hydrocarbon is cyclohexane.

15. The process of claim 1 wherein said aliphatic hydrocarbon is normal pentane.

16. The process of claim 1 wherein said reaction mixture additionally contains a methylenic ketone.

17. The process of claim 1 wherein said reaction mixture additionally contains methyl ethyl ketone.

18. The process of claim 1 wherein said reaction mixture additionally contains cyclohexanone.

19. The process of claim 1 wherein the reaction is carried out in a temperature range of about to about 200 C.

20. The process of claim 1 wherein the reaction is carried out in a temperature range of about to about C.

References Cited UNITED STATES PATENTS 3,467,698 9/ 1969 Schulz et al 260-524 3,215,733 11/1965 Mac Lean et al 260524 2,853,514 9/ 8' Brill 260-524 3,474,137 10/ 1969 Kudo et al 260524 JAMES A. PA'ITEN, Primary Examiner R. S. WEISSBERG, Assistant Examiner U.S. Cl. X.R. 260517 

